1. Technical Field
This system described herein relates generally to radiation protection systems and, more particularly, to radiation shielding systems integrated into procedural environments for use in the course of therapeutic procedures, for example, to radiation shielding systems integrated into procedural environments for use in the course of the performance of brachytherapy procedures as well as methods for the use of such systems.
2. Description of Related Art
Various techniques have been developed to treat tumors in the body. In general, the use of radiation to reduce or eliminate malignancy has been known for many years.
Brachytherapy is a method of radiation treatment of cancerous tissue in which the radiation source is placed in or near the cancerous tissue. Brachytherapy treatment permits administration of higher radiation dose to the tumor with better sparing of surrounding normal healthy tissues.
Temporary brachytherapy is a process whereby the radioactive sources are placed into the body, usually using an applicator, such as a needle, catheter or other tubular apparatus, for a limited period of time to deliver the requisite radiation dose, and then the sources are removed. With this treatment modality, applicators are prepositioned in the patient. The sources are later temporarily placed within them. This procedure is known as “afterloading”.
Temporary brachytherapy has been performed using a technique called “Low Dose Rate Brachytherapy”. Using this technique, radioactive sources are applied to provide a dose rate of 0.4 to 2 Gy/hour to the tumor. Using these techniques, treatment could require up to several days, during which period the patient remained hospitalized. Low dose rate techniques utilized a variety of radioactive isotopes, including 125Iodine, 137Cesium, 198Gold and 192Iridium.
There is also a technique for “High Dose Rate Brachytherapy” which uses a source to provide dose rates in the range of 2-7 Gy/minute. This technique permits the treatment to be performed in less than an hour, and without the hospitalization of the patient. Treatments may be delivered in multiple fractions over several days or weeks.
This high dose rate brachytherapy method employs a highly radioactive source that may be delivered via a catheter or other applicator appliance through a natural cavity, duct or vessel of the body directly to the tumor site for localized irradiation.
High dose rate brachytherapy may be performed using 192Iridium sources which have an initial activity of ˜10 Curies, although other radionuclides such as 169Ytterbium and 60Cobalt may be used. Such sources may produce dose rates of 6.8 Gy/min at 1 centimeter. Using such a source, high dose rate treatments may be 5-15 minutes duration.
Because of the very high dose rates associated with these sources, high dose rate brachytherapy treatments are often performed in shielded facilities to provide radiation protection to and reduce the radiation exposure of radiation oncologists, physicists, attending physicians, nurses, and other allied health personnel. Because of the panoramic emission pattern of the radiation from these high dose rate brachytherapy sources, this shielding may be designed to completely surround the radiation source.
These treatments may be performed in large shielded rooms with shielding on all sides as well as the floor and ceiling. Access to these rooms may be through large, heavy shielded doors, or through “maze”-type entrances. These rooms may require large amounts of floor space to house the patient, the treatment device and the treatment personnel who prepare the patient for treatment. Because of the large size of these rooms, the rooms may require an enormous amount of shielding material, which results in a relatively high cost.
It would be very attractive to provide this shielding in a more localized manner, as the volume of shielding required becomes less as the shielding is moved closer to the source of the radiation. It is therefore desirable to provide an improved design and method of fabrication and use for a shielded environment for the performance of temporary brachytherapy which would reduce the area required for its use, reduce the volume of shielded material required, and reduce the cost.
A fast growing application of high dose rate brachytherapy is accelerated partial breast irradiation (APBI), where a patient receives two fractions per day over a five-day period. The large number of prospective patients for this treatment protocol could tax the availability of existing treatment facilities, and could require the construction of new dedicated shielded treatment rooms. The shielding advantage of a localized shielding environment could facilitate the performance of breast brachytherapy in a much more moderately shielded room.
Of course, this could be accomplished by essentially “shrinking” the size of the room to a size just larger that the dimensions of the patient, essentially creating a shielded box around the patient. This could have the adversely effect of the comfort of the patient, by making the patient feel “closed in”, creating apprehension much like that one experiences during a closed magnetic resonance imaging examination. Therefore, it would be desirable to provide shielding in such a manner as to provide a visual open field of view to the patient beyond the shielding to reduce apprehension associated with a “closed-in” feeling.
Localized shielding environments have been used for other diagnostic and therapeutic applications, but none of these is arguably suitable for the very high radiation exposure rates and high gamma ray energies encountered in high dose rate brachytherapy.
Both fixed and mobile lead shields are employed in fluoroscopic procedures to minimize radiation exposure. Such shields may be constructed of radiation resistant plates that are interposed between the operators and the patient on an x-ray table. Despite the use of these shields, medical personnel are still exposed to radiation. Consequently, personnel also wear leaded protective clothing (including full lead aprons, thyroid collars and leaded glasses). These types of devices and clothing may not provide suitable or sufficient shielding for the very high radiation exposure rates and high gamma ray energies encountered in high dose rate brachytherapy.
There are patents teaching systems for protecting and shielding against radiation in x-ray laboratories, including various shields made of radiation resistant material that are either mobile or attached to the x-ray table and can be adjusted between the operators and the x-ray source. Such systems are described in various U.S. patents, including the following:                Egressi and Huszar, U.S. Pat. No. 1,907,523        D′Avella, U.S. Pat. No. 3,299,270        Mansker, U.S. Pat. No. 3,308,297        Volper, U.S. Pat. No. 3,924,374        Stivender, Lang and Mentink, U.S. Pat. No. 4,062,518        Bryant, U.S. Pat. No. 4,074,141        Lenhart, U.S. Pat. No. 4,581,538        Baudro, U.S. Pat. No. 4,638,166        Schukei and McDonald, U.S. Pat. No. 4,729,869        Lenhart, U.S. Pat. No. 5,006,718        Kobayashi, U.S. Pat. No. 5,090,044        Rubenstein, Pahira, and Taylor, U.S. Pat. No. 5,417,225        McAuley and Geiger, U.S. Pat. No. 5,981,964        Heesch, U.S. Pat. No. 6,325,538, and        Goldstein, U.S. Pat. No. 6,653,648        
Though there are numerous shapes and designs for shields, and although the shields may be constructed of various materials, the systems described in the patents listed above are all arguably directed to providing shielding from a source of radiation external to the patient and do not sufficiently protect against radiation exposure from a radiation source located within the patient. Accordingly, it is desirable to sufficiently reduced the primary and secondary radiation exposure of medical personnel in the vicinity of a patient undergoing high dose rate brachytherapy through the placement of very high exposure rate sources within the patient's body, and in particular, in such a way as to provide the patient with a wide field of view of the area outside the shielding.